More than 1.5 million people have now signed a Facebook page calling for a "storming" of Area 51, the secretive US military base in the Nevada desert on September 20.
If all goes according to plan those who turn up will run ninja-style into the facility, which has no fences around it, looking for signs of alien life being hidden by the US government.
If they don't all get shot what they might find is anyone's guess.
What is Area 51 really?
Area 51 is an assembly of buildings and an airstrip built around a salt flat called Groom Lake. It is part of the Nevada Test and Training Range, which is the biggest air and ground military testing area in the Western world, stretching over nearly three million acres. That's about twice the size of Devon.
According to the US military it is excellent for simulating a "flexible, realistic and multidimensional battlespace". They won't say much else about it.
In the mid-1950s the CIA began using the area to test U-2 spy planes, and later the development of the B-2 stealth bomber.
It was only in 2013 that the existence of Area 51 within the testing range was officially acknowledged.
The CIA was forced to release documents about it when Dr Jeffrey T. Richelson, an academic at George Washington University, successfully applied for information on the U-2 programme under the Freedom if Information Act.
Dr Richelson died in 2017. But at the time he told the New York Times there was an "overlap" between U-2 testing and UFO sightings.
"You had these high-flying aircraft in the air being the cause of some of the sightings,” he said.
How did Area 52 become synonymous with UFO sightings?
People in Nevada have reported them since the 1950s.
In June 1959 a local newspaper, the Reno Evening Gazette, interviewed a police officer who had seen something "bright green in colour, and descending toward the Earth at a speed too great to be an airplane."
Many more were to follow.
Then, the conspiracy theorists found a champion. In a 1989 television interview Bob Lazar claimed to have been a physicist working on “reverse engineering” of alien spaceships.
Lazar claimed to have worked at S4, a place just south of Area 51.
He claimed there were nine UFOs of differing types. One was like a “jello mould” and another like a flat disc.
They were allegedly fuelled by a substance called moscovium, which was used to create a gravity wave.
Aliens had been visiting Earth for thousands of years and came from a star system called Zeta Reticuli, he claimed.
Lazar has continued his claims. Speaking last year he described the inside of one of the UFOs thus: “It’s a very ominous feeling because everything is one colour. It’s like a dark pewter colour.
“There are no right angles anywhere. It’s as if somebody took a model and fashioned it out of wax and then heated it just for a short time so everything melted.
"Everything looks like it’s fused together. Everything has a radius, a curvature where two items meet. It’s a really weird looking thing."
He said one of them was "ancient” - perhaps 10,000 years old - and had been recovered from an archaeological dig.
Then Hollywood ran with it...
Hollywood became obsessed with UFOs.
From Simon Pegg and Nick Frost meeting an alien called Paul, to Will Smith learning to fly an alien spaceship at Area 51 - and punching an alien in the face. Mulder and Scully from the X-Files witnessed strange goings on at Area 51 too.
It has all led to a booming local alien tourism industry.
The “Extraterrestrial Highway” runs nearby and Rachel, Nevada has styled itself the “UFO Capital of the World”.
How did the plan to storm it come about?
It was a joke. But now some people are taking it seriously.
The Facebook page says: “They can't stop all of us. Let's see them aliens. We can move faster than their bullets.”
According to Jackson Barns, who started it: “Then the Rock Throwers will throw pebbles at the inevitable resistance (we don’t want to hurt them, we just want to annoy them enough to not shoot).
“P.S. Hello US government, this is a joke, and I do not actually intend to go ahead with this plan. I just thought it would be funny and get me some thumbsy uppies on the internet.”
Two nearby hotels are already booked up.
What is the military saying?
They are not amused.
A US Air Force spokesman said: "The United States Air Force is aware of the Facebook post. Any attempt to illegally access military installations or military training areas is dangerous.”
“We would discourage anyone from trying to come into the area where we train American armed forces.
“The US Air Force always stands ready to protect America and its assets.”
Thornton T. Barnes, a former intelligence officer who worked at Area 51, said: “In the real world, Area 51 is a remote rectangular no-fly area.
“The possibility of one million or more people storming Area 51 will require the participants to brave and survive trespass through an aerial gunnery and bombing range heavily utilised for electronic combat ranges, aircraft control and warning.
“In doing so, they must traverse ordnance impact areas in addition to the Air Force’s live-fire activities.”
He added: “There are no, and have never been, aliens or extraterrestrial craft at Area 51, period!” Even Bob Lazar thinks it’s a bad idea.
He wrote on Instagram: “I do not support this movement.
“The only place there was ever any alien technology was at Site S4, south of Area 51 proper. That was 30 years ago. S4 may have moved decades ago or it’s possible it’s no longer being used for the project."